S&S Cycle - Vintage Motorcycle TECH TALK

Pretty much anything not covered by the topics above. Short lived production bikes or vehicles, Electrical, Tires, Paint, Brakes, etc. Use this for tech questions, and "Shoot the Bull" for general conversation, no tech.

Thanks Panic and Patrick. The bike was purchased as is and it does run dual points with two separate 6 volt coils. No matter what we did with the two coils, we ended up with one dead cylinder. Since I asked this question, we installed a pair of 12 volt coils and electonic ignition. She is firing on both cylinders now. Pa

While touring in Mexico back in the '60's, I forgot to turn off my ignition when we stopped at a cantina in the desert. This fried one set of points, condenser, and coil. I one lunged into Mexicali and all I could find was a Yamaha dealer. Well as it turned out Yamaha was producing a 650 Vertical Twin that bore a strange resemblance to a '50's Limey bike. I bought one set of points, condenser, and coil, and it all bolted in to my '67 Booneville. Bike fired right up and ran great. When I got back to LA I pulled the plugs and found that the Yammy side was burning much better than the Lucas side. So I was off to the local Yamaha dealer to buy the other set.

Back when Gordon Jennings was at CYCLE they did a real eye opener of a coil test, and found that almost all foreign bikes were seriously under-coiled, and had borderline sparks which were responsible for much of their reputation for being hard to start etc. They did some miracle cures putting K-Mart Chevy coils on Ducatis, etc only to find out that in many cases they overloaded the electrical system. I built up a few coil systems for Vincents using the same coil, with greatly improved starting and low speed tractability.

BTW, there is often very little difference between a 6V and 12V coil. All coils are really 6v, and for 12 (or 24) they just add a ballast resistor to limit the current. GM traditionally used an external resistor, and Ford built them into the coil. So if you are stuck for a 6V coil, any 12V coil intended for use with an external resistor will work fine,